Conventionally, a hot water system has been used, in which water is heated by a heat pump unit and the hot water is stored in a tank.
The hot water system using a plurality of heat pump units has been proposed (refer to Patent Literature 1, for example). In the conventional hot water system, the number of heat pump units to be operated is determined according to the hot water supply load. The order of priority to start operation is specified for each heat pump unit. The order of priority is changed at every predetermined time period.
Patent Literature 1: JP2005-134062A